Frequency bands associated with various protocols are specified per industry standards for cell phone and mobile device applications, WiFi applications, WiMax applications and other wireless communication applications. As new generations of wireless communication systems become smaller and packed with more multi-band functions, design of new types of antennas and associated air interface circuits is becoming increasingly important. As the antenna's radiator becomes smaller and more integrated within the system, the impact on the antenna's impedance becomes significant, leading to a narrower bandwidth for a constant return loss. The narrow bandwidth in term of the return loss limits the power transfer to the antenna and the number of frequency bands that the antenna can support. It also reduces the robustness of the system since a communication system with an air interface tends to be affected by use conditions such as the presence of a human hand, a head, a metal object or other interference-causing objects placed in the vicinity of an antenna, resulting in impedance mismatch and frequency shift at the antenna terminal. A narrow frequency bandwidth makes the system sensitive to such phenomena. Accordingly, increasing the bandwidth has been one of the goals in many antenna designs. Conventional ways to achieve the goal includes the use of either a passive matching circuit made of distributed or discrete lumped components, or an active matching solution. A passive matching circuit tends to become inefficient and/or too complex when many components are used, while more and more components are needed in the matching circuit to match multiple frequency bands. An active solution provides more flexibility than the passive counterpart, but raises cost and complexity challenges as well as non-linearity and power consumption.